Twist drill point grinder



Dec- 10, l957 H. s A SIEMsEN :ri-Al. 2,815,610

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United States Patent" TWIST DRILL POINT GRINDER Henry S. Siemsen and Kenneth E. Foote, Los Angeles, Calif.

Application July 13, 1953, Serial No. 367,517

11 Claims. (Cl. 51-98.5)

This invention relates to a twist drill grinding machine, and more particularly to such a grinding machine which is automatic in its operation, so that the operator merely places the drill to be ground in a holding means and removes it therefrom after the grinding operations have been completed.

When twist drills become dull from use they must be ground to recondition them for efficient cutting. The generally followed practice of grinding drills by hand requires a high degree of skill acquired only by practicing for a considerable period of time, and even skilled workmen cannot hand grind drills in a uniform and altogether accurate manner. However, an investigation of the prior art discloses that it is not altogether new to use grinding machines to recondition dull twist drills, some of such machines being to a certain extent automatic in their operation. Nevertheless there remains ample room for improving upon such machines, particularly in regard to providing a machine which is usable in grinding drills of different helical twists, in rendering the machine more fully automatic in its operation, and in the provision of a simpler, more compact mechanism for automatically performing, in proper sequence the required drill positioning, drill moving and drill grinding operations.

Accordingly, among the objects of the present invention are: to provide a drill grinding machine which is usable to grind points of drills having different helical angles, and. in which no adjustment of the machine is necessary in changing from sharpening a drill of a certain helical angle to the use of the machine to sharpen a drill of a different helical angle; to provide a machine for drill point grinding which will require less skill for its eilicient operation and wherein all the operations except the insertion and removal of the individual drills are automatically performed; and to provide for a more rapid, automatic drill point grinding.

A more specific object is to provide an improved means for accurately placing each drill in the proper rotational position for having its point portion ground.

Other objects, advantages and features of invention will hereinafter appear.

Referring to the accompanying drawings, which illustrate a preferred, reduced to practice embodiment of the invention,

Fig. l is a front elevation of the machine, the automatically moved parts thereof being shown positioned for commencing a drill point grinding operation.

Fig. 2 is a plan View of the machine with the operating parts in the same position as in Fig. 1.

Fig. 3 is a fragmentary side elevation illustrating the means which automatically rotates the drill through an arc of 180 degrees after one side of the point portion Y-thereof has been ground, said means being shown positioning the drill for the second grinding operation.

Fig. 4 is a horizontal midsection on line 4 4 of Fig. 2 of the drill point positioning means, showing the saine in its extended position preparatory to inserting a drill for grinding.

Fig. 5 is a left side elevation of the machine with the various parts thereof positioned as shown in Fig. l.

Fig. 6 is a fragmentary side elevation showing the positions various co-operating parts assume when the drill reaches the grinding position.

Fig. 7 is an elevation of the reverse side of the structure shown in Fig. 6.

Fig. 8 is a fragmentary section on line SS of Fig. l, of the drill holding chuck and adjacent parts, a drill being shown loosely positioned in said chuck.

Fig. 9 is a front elevation showing part of the structure illustrated in Fig. 8, the drill being omitted.

Fig. 10 is a longitudinal, vertical section on line lll-40 of Fig. 2, illustrating on an enlarged scale a portion of the drill rotating means fragmentarily shown in Fig. 3.

Fig. ll is a View, on the same scale as Fig. l0, additionally illustrating the positioning of the point portion of a drill to be ground, a fragment of which is shown.

Fig. l2 is an end view of a drill of the type operated on by the machine.

Fig. 13 is a perspective View of an adjustable chuck jaw member which forms a part of the drill gripping means.

Referring in detail to the drawings, the mounting means shown by way of example, comprises a basal support 25 provided with suitable legs 26. As viewed in plan said support is of a stocky T shape, the crosshead of the T being a channel member 27 the flanges 7.8 and 2.9 of which are downwardly directed, the stem of the T also being channel shaped, with downwardly extending side flanges Elli, the midlength portion of the aforesaid flange 29 being welded at 31 to an otherwise open end of said T stem structure.

Upon the stem portion of the aforesaid T-shaped mounting means is mounted an electric motor 35 to the drive shaft 36 of which is secured an abrasive wheel 37 used to grind the drills.

Upon one end portion of the aforesaid cross bar 27 (the front part, the part thereof nearest to the operator), is mounted an elongated `cross slide base 40, dovetailed onto the upper side of which to slide longitudinally thereof is the lower track portion 4l of a cross slide member 42, the upper, right angularly disposed -track portion 43 of said member 42 having adjustably dovetailed onto it the basal portion 4S of a horizontal mounting plate 46. The aforesaid cross slide structure is of a conventional character and, therefore, need not be further described except to say that it is provided with the usual lower shaft 48 carrying a crank 49 and upper shaft fill carrying a crank 5l, the latter shaft being usable to adjust said mounting plate 46 from front to rear and vice versa, While said shaft 48 is used to adjust said plate toward one side or the other. Other suitable adjustable mounting means may be substituted for this structure, if desired.

Said mounting plate 46 rockably supports, in an intermediate manner, an upstanding member 5S. The preferred immediate mounting means for said member 55 is an auxiliary base member 56 secured in any preferred manner to the upper face of the mounting plate 46, the latter plate being shown provided with two intersecting undercut grooves 57 and 58 one or both of which may be used to receive the heads of suitable bolts (not shown), whereby said auxiliary base is secured to said base plate 46, said bolts extending into threaded sockets in hexagonal clamping pins 59.

Said auxiliary base 56 carries upstanding therefrom and preferably cast integrally therewith, housing 6l? and, spaced away from said housing an upstanding bearing lug 61. For convenience of illustration said housing is shown in Figs. 5 and 6 with an open front side, which in practice may be suitably closed. Said housing co-operates with said lug to form bearing means for a short, horizontal rock shaft 63, one end portion of this shaft extending into said housing and there having secured to it one end portion of a movement transmitting arm 65.

Between said housing and the aforesaid 'bearing lug 61 said rock shaft has secured to it the lower end portion of the aforesaid upstanding rockable member 55. The upper end portion of this member is horizontally extended at each side thus forming a T-shaped structure which carries two substantially parallel air cylinders 70 and 72 which are in a xed relation to the crosshead of the T structure. Said cylinders 70 and 72 extend horizontally, and along the crosshead of the T-shaped structure which carries them, cylinder 70 having a piston werking in it having a rack toothed projecting end portion or stern 73 the teeth of which are downwardly directed and mesh with a gear 75. A spring 73a retracts said rack when permitted to do so, one end of said spring being anchored to the upper part of the rocking arm 55.

Said gear 75 forms a part of the mechanism for turning each drill 76 being ground through an angle of 180 degrees after the rst half of the grinding operation has been performed, so that both lips of the point portion of the drill will be accurately ground by the aforesaid motor driven abrasive wheel 37. Said gear 75 is tightly secured to a circular lateral projection 75a carried by a turnable tubular body 77. The bearing means for said gear and body comprises a tubular bushing carrying member 79 of two diameters, a removable bushing 78 being snugly fitted within the part of said member 79 which is of the larger diameter. The part of said bushing carrier which is of the larger diameter is fitted with a press tight fit within a bore 79b provided for it, said bore extending through the adjacent part of the crosshead of the aforesaid rockable member 55. A set screw 80 positioned as shown in Fig. 8 is used to hold said bushing in place, said set screw being carried by the upper portion of the rockable member 55 and extending through an aperture provided for it in the diametrically larger portion of the aforesaid bushing carrier. A ball bearing structure 82 is provided to facilitate the turning movements of the aforesaid tubular member 77, and the diametrically smaller part of the aforesaid bushing carrier 79 is fitted with a press tight lit within the inner part of said ball bearing structure.

Said body 77 has through it a diametrical bore 85 an end portion of which is screwthreaded `and contains an abutment screw 86 locked in adjusted position by a set screw 87. Said abutment screw 86 acts against a generally cylindrical chuck jaw member 88, a flattened strip 88a of which is engaged by a set screw 89. Said member 88 has a broadly V-shaped end portion 88b which is engaged by the gripped drill. When said member 88 is adjusted by means of the abutment screw 86, the screw 89 is only slightly loosened so as still to maintain the jaw member 88 in the proper rotational position. The opposite end portion of said bore slidably contains a piston rod 90 of a piston having a head 91 working in a piston chamber formed by a hollow enlargement 92 of the aforesaid body 77. An air supply means for operating said piston will be described later. At the inner side of its bore 85 said body 77 has a bore 94 which alines with and is of the same diameter as the bore into which is fitted the bearing member 78, and alining with said bore 94 said body has a slightly larger bore 95 at the opposite side of said bore 85.

Describing in further detail parts associated with the aforesaid air cylinder 70, as illustrated in Fig. l0, there a fragment 55a of the crosshead of the supporting member is shown having a sleeve portion 55b enclosing said cylinder with a press tight lit. Said cylinder has screwed onto one of its ends a ca'p 70C which is provided with a suitable central opening through which the toothed stern 73 operates, this `cap being shown in an abutting relation both to the end of said cylinder and to the aforesaid sleeve portion b. Said stem 73 has secured to its inner end a piston head 73a, the outward movement of which is limited by an adjustable stop screw 73b carried by a titting 100 which is screwed onto the adjacent end of the cylinder in an airtight manner and laterally from which projects an apertured boss b through which air under pressure is forced into the cylinder and though which the air is at the proper times allowed to escape from said cylinder.

Referring more particularly to Fig. 4, the device for enabling the operator to turn each inserted drill to the proper position for having its point portion ground, comprises the already mentioned piston cylinder 72 containing a piston rod 95 having secured to its midlength portion a collar 96 against which abuts a compression spring 97. Said piston structure includes an outer jacket 98 and an inner tube 99 having a lateral tubular air supply branch 99a through which air enters to retract the piston against the opposition of said spring. This piston structure is also shown as comprising an apertured, ordinarily proportioned cap 101 screwed onto one of the end portions of said tube, an elongated apertured cap 103 being screwed onto the opposite end of said tube 99. Said piston rod extends through the apertures of said caps and is provided with a double nut 104 forming a stop to arrest the spring impelled movement of the piston rod, by abutting against said cap 103. Also an adjusting nut 105 is screwed onto said tube 99, said nut abutting said cap 103 against which one end of the spring abuts, thus locking in place the means for regulating the tension of the spring. An O-ring structure 106 is fitted within the tube 99 in an operative relation to the piston rod 95'.

At its right hand end as viewed in Fig. 4 the piston rod 95' carries a head 108 (see also Fig. 11), usable by the operator rotationally to adjust the drill before the grinding thereof is begun. As shown in Fig. 11 this head comprises a projection 109 which is engaged by the apex of the drills point to arrest the sliding of the drill into place within the chuck structure which has already been mentioned. Said head 108 is also provided with an angular stop member 110 (see also dotted lines of Fig. 12), which is so positioned that, when the operator, after bringing the apex of the drills point into contact with said member 109, turns the drill in an anti-clockwise direction, a side of one or the other of the two grooves 111, 112 of the drill engages said stop member 110, thus arresting anti-clockwise turning of the drill with the point thereof in the proper position for being ground.

In addition to the aforesaid air cylinders carried by the rockable arm 55 a stationary air cylinder 115 is provided which is shown upstanding from the top of the rear portion of the aforesaid housing structure 60. Said cylinder 115 (well shown in Fig. 6), may be attached to the housing 60 by screws, not shown. This cylinder contains a piston 118 the downwardly projecting rod or stem 119 of which abuts the free end portion of the aforesaid arm 65 which rocks rearwardly the upstanding T-shaped member 55 and parts carried thereby. This rearward rocking of the arm or member 55 is opposed by a tension spring 121 anchored to the forward hexagonal clamping pin 59 carried by the aforesaid auxiliary base 56, said member 59 carrying also an adjustable stop screw 123 carrying a head 123x which limits the forward swing of the arm 55. A similar stop screw 123a carried in the rearward clamping pin 59, limits the rearward movement of the arm 55 and determines the amount of metal which will be ground from the drill tip.

The means for supplying air under pressure to the aforesaid air or piston cylinders at properly timed intervals and in the proper sequence comprises an encased timing mechanism shown 'carried by the lower part of the leg supported main mounting means. Also a compressed air supply pipe line is furnished with branch pipes whereby are supported a series of three solenoid operated valves 140, 141 and 142, of the type manufactured by Automatic Switch Co., Orange, New Jersey, and identified as Bulletin 8314, Three Way Valves, these valve and solenoid combinations or valved fixtures being indicated in a somewhat diagrammatic manner in Fig. 5, where dual current cables 143, 144 and 145 lead from the timer respectively to said valves.

yIn regard to the flexible air conduit means used, from said valve 141i an air hose 146 leads to the aforesaid stationary air cylinder 115, from said Valve 141 a hose 147 leads to a point superjacent to the aforesaid rockable mounting member 55 where said hose 147 is, in eect, branched, so as to terminate in the hose sections 148 and 149, the former hose section communicating with the cylinder 72 and the latter with the cylinder 77.

From the valve 142 a hose 153 leads to the cylinder 70.

Upon the left end portion of the crosshead 27 of the main T-shaped support is mounted a wheel dresser device 170 of a universally adjustable character. This device carries a diamond tipped cross bar 171 which is adjust- :able to extend across the periphery of the abrasive wheel 37 to true it up to the proper angle. This wheel dresser may be swung down to a horizontal position as shown in dotted lines in Fig. 2. It forms no part of the present invention, but has been briefly described because of being an adjunct which enables the workman to use the invention to better advantage.

Operation In grinding a drill, starting with the air shut-olf from all the air supplied cylinders, the drill is inserted from front to rear through tube 78 until the insertive movement thereof is stopped by the stop member 109 of the drill locator 105. Thereupon the operator will turn the drill in clockwise direction until the aforesaid stop projection 110 (see Figs. ll and l2), arrests such turning movement when the drill has reached the rotational position required for the proper grinding thereof. This is an important step in the operation of our improved drill point grinding machine because it positively insures accurate drill point location so that the point portion of the drill is ground in an angularly accurate manner regardless of variations of the helical twists of different drills. The timing mechanism gives a very brief interval for this to be done by the operator, and then supplies energizing current to the solenoid 141, thus causing air to pass through hose 147 into air cylinder 92, thus causing piston rod 9d to grip the drill between itself and the chuck jaw member 38, the air also at the same time being let into cylinder '72 and causing the piston thereof to retract the drill locator 108 so it will not interfere with the machine bringing the point of the drill into contact with the emery wheel. Then the timer causes the solenoid 149 to be energized, thus delivering air to the cylinder 160 through a llexible hose 1601/1 (which branches off from hose 146), and causing the stabilizing pin 161 to be brought into contact with the adjacent side of the clutch gripped drill. Thereupon the timer causes air to be admitted to the stationary piston cylinder 115, which causes the piston thereof to act upon the arm 65 carried by the rock shaft 63, thus rocking the rock shaft and causing the arm 55 and the parts it carries to swing toward the emery wheel, thus bringing the point portion of the drill into a grinding contact with the emery wheel.

Then the timer releases the air in the stationary cylinder 115, whereupon the arm 55 is spring retracted to normal position by spring 121. Thereupon the timer releases the air pressure from the cylinder 160, allowing a spring to retract the stabilizing pin 161 from the drill, whereupon the timer supplies current to the solenoid 142 and air is admitted through hose 153 into cylinder 70 causing the rack to turn the drill holding chuck through 180 degrees. (This turning movement of the chuckgripped drill in a clockwise direction and later in an anticlockwise direction occurs each time during a very brief interval which follows each swing of the member 55 away from the abrasive wheel.) Thereupon the timer causes the solenoid to be energized, thus again delivering air to the cylinder and causing the stabilizing pin 161 to be again brought into contact with the adjacent side of the clutch gripped drill. Thereupon the timer supplies air again to the stationary cylinder 115 to rock the arm 55 and the parts carried by it forward to the drill grinding position.

Next the solenoids 140, 141 and 142 are all de-energized allowing the air to exhaust from all the cylinders so that the various retracting springs function to restore all parts to starting position, and also the drill is released from the chuck by a coil spring retracting the piston rod 90.

In handling the smaller sizes of drills the whole drill grinding cycle can readily be completed in six seconds, but it is desirable to allow a longer time for the cycle when larger drills are ground, it being one of the merits of our machine that it can be used to perform efficient drill point grinding operations at a great variety of speeds.

The drill stabilizing means which has been described is not vital to efcient drill grinding, but has been found to improve the operation. Each time air is directed into the stationary cylinder 115 said stabilizer encounters the side of the drill and holds the drill iirmly against the opposite side of the drill holding tube 78. This arrangement compensates for wear on the tube which guides the drill during grinding thereof.

The complete timing mechanism comprises six conventional timing oscillator circuits, the operation of each of which energizes a relay to open and close for contacts. One of the oscillator circuits is shown in Fig. 14, while the relationship between the circuits and contacts is shown in Fig. l5.

We claim:

1. In a machine yfor grinding the point portions of twist drills, a basal support, a motor-driven abrasive wheel mounted thereon, an upstanding rockable member mediately carried by said support adjacent to said abrasive wheel so that, when said member is rocked the upper part thereof approaches and recedes from the periphery of said wheel, a normally -open chuck structure carried by the upper part of said member in a position to grip a drill with its point directed toward the grinding surface of said wheel, said chuck structure comprising a stationary jaw member and a piston structure comprising a cylinder and a pist-on therein having a stem portion which constitutes the movable jaw of the clutch structure, a drill locating means comprising a part which at times engages the point portion of the drill to be ground, said drill locating means also including a piston cylinder having therein a piston the stem of which carries said drill point engaging part, pneumatically operated means operatively connected with said rockable member to swing the same toward and from said abrasive wheel, a compressed air supply including flexible hose connected with the aforesaid piston cylinders, combination valves and solenoids carried by said basal support and positioned to control the supply `of air under pressure to said cylinders to operate the pistons in them and to control the supply of air to operate said pneumatic means, electric conductors arranged to supply current to the solenoids of said valves to open them when required, and a timing device operatively connected with said conductors, said timing device operating the aforesaid solenoid and valve combinations to control supply of air under pressure to said cylinders and pneumatic means in the proper sequence and at the proper intervals, so that said drill point locator arrests the insertive movement of a drill when the aforesaid rockable arm is in its retracted position in relation to said abrasive wheel and retracts said drill point locator out lof the way of the drill before said rockable =arm is pneumatically moved toward said abrasive wheel to bring the drill point into a position to be ground, springs carried by said rockable member and arranged to act upon said pistons in opposition to the air supplied to them, and a retracting spring operatively connected to said basal support and rockable member.

2. In a machine for grinding the point portions of twist drills, basal supporting means, a movable member mounted on said supporting means for movement toward and from a rotating abrasive wheel, mechanically ltimed means operatively connected with said member to move it as aforesaid, a chuck carried by vsaid member to grip a drill with its point directed toward said wheel to come into grinding contact therewith when said member is moved as aforesaid toward said wheel, said chuck being turnably mounted on said member so Yas to be turnable about an axis concentric to the axis of the gripped drill, and automatic means mounted on said movable member and operatively connected with said timing means to turn said chuck and gripped drill through an angle of 180 degrees after one side of its point portion has been ground so that, upon a following movement` of said movable member toward the abrasive wheel the diametrically opposite part of the point position of the drill will be ground.

3. In a machine for grinding the point portions of twist drills as defined in claim 2, said chuck turning means comprising a gear carried by the chuck concentrically of the gripped drill and a pneumatically operable piston mounted upon said movable member and having a stem with a rack portion in engagement with said gear.

4. In a machine for grinding the point portions of twist drills, basal supporting means, a movable member mounted on said supporting means for movement toward and from a rotating abrasive wheel, mechanically timed means operatively connected with said member to move it as aforesaid, a chuck carried by said member to grip a drill with its point directed toward said wheel to come into grinding contact therewith when said member is moved as aforesaid toward said wheel, said chuck being operatively connected with said mechanically timed means so that the chuck remains closed during the grinding of each drill and is caused to open after the grinding of the drill has been completed, and a chuck turning means carried by said movable member and operatively connected with said mechanically timed means to turn said chuck and a drill gripped thereby through an angle of substantially 180 degrees after every movement of said movable member away from the abrasive wheel.

5. In a machine for grinding the point portions of twist drills as defined in claim 4, said chuck turning means being pneumatically operated both when performing the opening and closing and turning movements of said chuck, and flexible air conducting tubing connecting said mechanically timed means with a source of compressed air supply.

6. In a machine for grinding the point portions of twist drills, a basal support, a member carried by said support and movable toward and from a rotating abrasive wheel, a normally open chuck carried by said member in a position to grip a drill with its point directed toward the grinding surface of said wheel, said chuck comprising an adjustable stationary jaw structure, a mos/able jaw structure forming a part of said chuck and including a cylinder having a piston therein the stem of which ,forms a jaw element to co-operate with said stationary jaw, drill point locating means carried by said mediately carried movable member, and spring opposed pneumatic means controlled by a timing device and operatively connected with said movable member, chuck structure and drill point locating means to operate all of them in a properly timed manner so that said chuck grips the drill during the movements of said movable member toward the abrasive Wheel, and said drill point locating means is moved into the space between the point portion of the drill and the abrasive wheel before each movement of the drill toward the wheel, and is moved out of said space before the drill nears vsaid wheel.

7. In a machine for ygrinding the points of drills, a rotatable grinding wheel, a basal support, a movable member mounted for movement with respect to said grinding wheel, a chuck carried by said member to grip a drill with its Vpoint directed toward said wheel, means for automatically and sequentially moving said chuck and drill toy bring lone side of said drill into grinding contact with said grinding wheel and then out of contact therewith, rotating said chuck and drill through an angle of moving said chuck and drill to bring the opposite side of said drill into grinding contact with said grinding wheel and then out of contact therewith, said means cornprising a plurality of hydraulically operated cylinders, at least one of said cylinders controlling each of said movements, a source of hydraulic pressure fluid connected to each of said cylinders, at least one solenoid valve interposed between each of said cylinders and said fluid source, and means for controlling the operation of said solenoid valves to control said movements.

8. In a machine -for grinding the points -of drills, a rotatable grinding wheel, a basal supporting means, a movable member mounted for movement with respect to said grinding wheel, a chuck carried by said member to grip a drill with its point directed toward said wheel, means for automatically and sequentially moving said chuck and drill forwardly to bring one side of said drill int-o grinding contact with said grinding wheel and then backwardly out of contact therewith, rotating said chuck and drill ythrough an angle of 180, moving said chuck and drill forwardly to bring the opposite side of said drill into grinding Contact with said grinding Wheel and then backwardly out of contact therewith, said means comprising a plurality of hydraulically operated cylinders, at least one of said cylinders controlling each of said movements, a source of hydraulic pressure fluid connected to each of said cylinders, at least one solenoid valve interposed between each of said cylinders and said fluid source, and means for controlling the operation of said solenoid valves to control said movements.

9. In a machine for grinding the point portions of twist drills, a basal support, an upstanding rockable member mediately carried by said support for movement toward and from an abrasive wheel so that when said member is rocked the upper part thereof approaches and recedes from the grinding surface of said wheel, a normally open chuck structure carried by the upper part of said member in a position to grip a drill with its point directed toward the grinding surface of said wheel, pneumatically operated means carried by said rockable member to open and close said chuck structure, pneumatically operable means carried by said basal support to rock said arm, said pneumatic means including valves to control air supplied under pressure, automatic means operatively vconnected with said valves to open and close them in proper sequence to in succession grip drills manually inserted one at a time into said chuck structure and then swing said rockable member toward the abrasive wheel to contact the drill points therewith for grinding, a spring connected with said chuck to open it after its said pneumatic operation, a spring connected with said rockable member to swing it away from said abrasive wheel after each movement of said member toward said wheel, a pneumatically operated drill stabilizer carried by said rockable member in a position to be moved into lateral engagement with each inserted drill between the point of the drill and said chuck, a valve to control the supply of air under pressure to pneumatic means which operate said stabilizer, said valve being controlled by said automatic means, and a spring to retract the said stabilizer from the drill whenever the air pressure is released.

10. In a machine for grinding the points of drills, a rotatable grinding wheel, a basal support, a movable member mounted on said support for movement with respect to said grinding wheel, a chuck carried by said member to grip a drill with its point directed toward said wheel, a drill stabilizer adapted to contact said drill to prevent undesired movement thereof during the grinding of said drill, means for moving said drill stabilizer, comprising a hydraulically operated cylinder, a source of hydraulic pressure fluid connected to said cylinder, a solenoid valve interposed between said cylinder and said fluid source, and means for controlling the operation of said solenoid valve to control the' movement of said drill stabilizer to automatically move said drill stabilizer into Contact with said drill before the grinding operation and to automatically move said drill stabilizer away from contact with said drill after the grinding operation.

11. In a machine for grinding the point portions of twist drills, a basal supporting means, a movable member mounted on said supporting means for movement toward and from a rotating abrasive wheel, mechanically timed spring opposed means operatively connected with said member to move it toward said Wheel, a normally open chuck carried by said member and usable while open to guide the drill during manual movement thereof toward a position upon said movable member for being ground, a drill point locating means positioned to stop the insertive movement of the drill, said drill point locating means carrying a part positioned to stop clockwise manual rotation of the inserted drill when a side portion of a spiral groove of the inserted drill contacts with said stop member, said chuck being turnably mounted on said movable member so as to be turnable about an axis concentric to the axis of the gripped drill, a timing device, and automatic means mounted on said movable member and operatively connected with said timing device to turn said chuck and gripped drill through an angle of degrees after each movement of said movable member away from the abrasive wheel.

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